Selective Adsorption Of Metal Ions Research Articles

Hardness of surface hydroxyls and its pivotal role in the flotation of cassiterite from quartz via lead ions activation

Current research has trouble explaining the selective flotation mechanism realized by metal ions, which hinders the advancement of effective flotation techniques. In this work, the selective activation flotation of cassiterite from quartz with Pb2+ is taken as an example to illustrate the pivotal roles of surface hydroxyls in selective flotation. Accordingly, flotation, adsorption amount, and X-ray photoelectron spectroscopy (XPS) measurements and systematic first-principles calculations have been used to investigate the roles of hydroxyl groups on the selective adsorption of Pb2+. The obtained flotation, adsorption amount, and XPS test results consistently show that the Pb2+ can more strongly interplay with cassiterite than quartz resulting in selective flotation of cassiterite from quartz. The electron localization functional results illustrate that the electron localization of oxygen of Si-O bonds is stronger than the Sn-O bond resulting in the weaker electron migration ability (high hardness) of oxygen atoms of quartz than oxygen atoms of cassiterite. This makes the cassiterite surface hydroxyl groups less hard than quartz. Further crystal orbital Hamilton population and partial density of states show that the Pb2+ interacts with the oxygen atoms on cassiterite forming chemical bonds before and after the adsorption of benzohydroxamic acid (BHA). On the other hand, the interaction of Pb2+ with quartz is physical in the presence of BHA. The strong adsorption of Pb2+ on cassiterite makes it easier for BHA adsorption which accounts for the selective flotation of cassiterite from quartz. This work sheds new light on establishing a consistent and dependable theory that the hardness of surface hydroxyls is the original factor affecting the selective adsorption of metal ions on oxide mineral surfaces.

Enhanced selective adsorption capacity of lead (II) from complex wastewater by aminopropyltriethoxysilane-functionalized biochar grafted on the MXene based on anion-synergism

The simultaneous elimination of dyes and metal ions from wastewater is essential for industrial wastewater treatment. In the current work, a novel adsorbent, aminopropyltriethoxysilane-functionalized biochar grafted on MXene (APTES/BC/MXene composite), was synthesized and utilized to increase the selectivity of the uptake of lead from a complex multi-metal solution based on anion-synergism. The surface area of the APTES/BC/MXene composite (164 m2/g) was higher as compared to the BC (90 m2/g), APTES (87 m2/g), and APTES/BC (151 m2/g). The outcomes of selective adsorption of metal ions were altered by the composite before (APTES = 52.98 mg/g, APTES/MXene = 58.65 mg/g, and APTES/BC = 313.86 mg/g) and after grafting aminopropyltriethoxysilane-functionalized biochar on the MXene (APTES/BC/MXene = 323.17 mg/g). In this investigation, the composite showed remarkable selectivity for the adsorption of lead. The adsorption capacity of composite for Pb2+ (323.17 mg/g) was superior compared to Cd (16.45 mg/g), Sr (10.99 mg/g), Zn (25.37 mg/g), Ni (7.82 mg/g, Ca (20.79 mg/g), and Ag (58.47 mg/g). Interestingly, the selective uptake of lead by the composite was enhanced from 446.85 to 1072.04 mg/g as coexisting methyl blue dosages increased from 0 to 100 mg/L at a pH value of 6.0. In the lead-methyl blue complex binary system, lead and methyl blue indicated synergistic phenomena, in which the existence of methyl molecules generated new unique sites for lead adsorption, while methyl blue uptake was also increased by the existence of lead. The experiment's findings demonstrate that the prepared APTES/BC/MXene exhibited excellent stability and regeneration capabilities (96.2% and 95.1% adsorption efficacy after 5th cycles for Pb2+ and MB respectively), suggesting it can be employed as a quick and efficient uptake adsorbent for the elimination of MB and Pb2+ in a single pollutant system. Hydrogen bonding, electrostatic interaction, synergistic penetration, and ion exchange processes were primarily involved in the uptake of lead and methyl blue. This investigation offers useful insights for the development of composite that indicate outstanding performance and easy recovery for the synergistic and simultaneous uptake of heavy metal ions and organic dyes. The results also reveal the remarkable enhancement of selective heavy metal uptake from complex wastewater by utilizing anion-bye interactions.

Carbon quantum dots-containing poly(β-cyclodextrin) for simultaneous removal and detection of metal ions from water

This study investigates the synthesis and characterization of supramolecular composites composed of poly(β-cyclodextrin-co-citric acid) and carbon quantum dots (QDs). These composites serve a dual purpose as adsorbents and photoluminescent probes for divalent metal ions, including Ni(II), Cu(II), Cd(II), and Pb(II), which can have detrimental effects on the environment. Various characterization techniques were employed to confirm the successful synthesis of the composites and the interaction between cyclodextrins and QDs. By using mathematical tools, optimal conditions for metal adsorption were determined, resulting in the composites exhibiting high adsorption capacities, reaching 220 mg/g, and impressive removal efficiencies exceeding 90 % for Ni(II) and Cu(II). The supramolecular composites also exhibit selective adsorption of metal ions with small ionic radio and can be reused with minimal loss of efficiency. In addition to their adsorption capabilities, these composites display luminescence quenching upon the adsorption of metal ions, which can be utilized for sensing applications. Spectroscopic evaluation reveals Stern-Volmer quenching constants for the accessible fraction of QDs in the range of 3777 to 13,359 M−1. The high stability of QDs on the composites allows for long-term storage. In summary, this original supramolecular composite shows promise for simultaneously monitoring and treating water and wastewater, making it a valuable tool in environmental applications.

Preparation of Pectin–Acrylamide–(Vinyl phosphonic acid) hydrogel and its selective adsorption of metal ions

Preparation of Pectin–Acrylamide–(Vinyl phosphonic acid) hydrogel and its selective adsorption of metal ions

Selective adsorption of metal ions on Salix psammophila fibre activated carbon

As an adsorbent of metal ions, activated carbon is often used to purify sewage. However, activated carbon fibres typically show similar adsorption capacity for different metal ions. Salix psammophila fibre (Spsf) was used as raw material to prepare activated carbon fibres (SP-FAC). This was modified with nitric acid (HNO3) to obtain HNO3-SP-FAC (FACHNO3). At 65 wt% concentration of HNO3, the impregnation ratio was 1:35 during 12 h, at 100 °C drying temperature, and the adsorption effect of FACHNO3 on Pb(II) was the best. At CHNO3 = 75 wt%, the impregnation ratio was 1:25. After an impregnation time of 36 h at the same drying temperature, the effect of FACHNO3 on Mn(II) was the best. At CHNO3 = 55 wt%, the impregnation ratio was 1:35, impregnation time was 36 h at 120 °C drying temperature, and the adsorption effect of FACHNO3 on Zn(II) was the best. These results indicate the existence of a close relationship between the pore structure of activated carbon fibres and the adsorption capacity of metal ions, and that the control variables changed the pore structure of activated carbon fibres so that it can achieve a competitive adsorption effect for different ions.

Insights into selective adsorption mechanism of copper and zinc ions onto biogas residue-based adsorbent: Theoretical calculation and electronegativity difference

Modified biomass-based adsorption technique has attracted much attention in heavy metal ions removal, but selective adsorption behavior and mechanism of heavy metal ions adsorption onto biosorbent still need to be further clarified. Herein, a carboxylated biogas residue (BR-COOH) was prepared to remove the Cu2+ and Zn2+ from single/binary heavy metal ions solution and explore selective adsorption mechanism. The results exhibited that the adsorption capacities of BR-COOH for Cu2+ was higher than that for Zn2+ obviously, whether in the single or binary heavy metal ions solution. Meanwhile, the introduced carboxy groups were identified as the main sites for metal ions adsorption. Density functional theory (DFT) calculation results exhibited that the adsorption energy of Cu2+ (-0.51 eV) onto BR-COOH was lower than that of Zn2+ (-0.47 eV), indicating that the Cu2+ adsorbed on BR-COOH was more stable than Zn2+. Moreover, the metal ions adsorption capacity of BR-COOH was positively correlated with their electronegativity, which was due to that the metal ions with stronger electronegativity was more easily interacted with the negatively charged oxygen in carboxyl groups. The same results were also verified in the control experiment conducted with two other biosorbents. Therefore, the work provided a new and in-depth insight into selective adsorption of metal ions onto carboxylated biosorbent.

Chelation dependent selective adsorption of metal ions by Schiff Base modified SBA-15 from aqueous solutions

Abstract Mesoporous silica SBA-15 was modified with Schiff bases of 2-hydroxybenzaldehyde (2-HB) or 4-hydroxybenzaldehyde (4-HB), after silanization with (3-aminopropyl)triethoxysilane (3-APTES). The obtained heterogeneous Schiff bases (2-HB-SBA-15 and 4-HB-SBA-15) were analysed using sophisticated characterization techniques to disclose their successful formation and physico-chemical properties. Whether chelation plays any key role in the selective adsorption of metal ions was evaluated using aqueous mixtures containing Mn(II), Co(II), Ni(II), Cu(II), Cr(III), Zn(II), Pb(II) and Cd(II) ions in the pH range 2−6. Both materials exhibited different affinity towards metal ions from the same mixture under various pH conditions. 2-HB-SBA-15 exhibited 100 % selectivity towards Pb(II) ion at pH 2 while the selectivity turned to Cu(II) at higher pH. 4-HB-SBA-15, however, showed an affinity towards Cr(III) and Pb(II) at pH 2 while a distributed selectivity was observed with major portion to Cr(III), Pb(II) and Cu(II) at higher pH conditions. The observed affinity towards a particular metal ion was enhanced when considering the Cr(III), Pb(II) and Cu(II) ions in single and double concentrations in the mixture at pH 5. When analyzing the structure of both organic molecules, 2-HB-SBA-15 has a chelation possibility but 4-HB-SBA-15 has less. The difference in molar adsorption selectivities of the two organically modified mesoporous materials, 2-HB-SBA-15 and 4-HB-SBA-15 clearly indicates the effect of chelation in ligand over selective adsorption of metal ions from aqueous mixtures at identical adsorption conditions.

Macrocyclic host appended carbon nanotubes for selective adsorption of metal ions: combined experimental, DFT and MD studies

Crown ethers are very useful for metal ion recognition due to their nanocavity based specific ion selectivity, which on functionalization with carbon nanotubes (CNTs) can be employed as specific metal ion filters by exploiting their different interactions with metal ions.

Melamine-Sulfonic Acid Functionalized SBA-15 for Selective Adsorption of Metal Ions from Artificial Seawater and Wastewater

Melamine-Sulfonic Acid Functionalized SBA-15 for Selective Adsorption of Metal Ions from Artificial Seawater and Wastewater

Superhydrophobic Hybrid Micro‐Nanocomposites with Various Applications

SummaryNovel bio‐inspired superhydrophobic hybrid micro‐nanocomposites were prepared by using plant or tree leaf powder as a bio‐source with the help of polysiloxane and various silane precursors. The hybrid suspensions showed superhydrophobic property when coating on various substrates by simple evaporation of solvents on the substrates at room temperature. Similarly, the hybrid powders obtained by the complete evaporation of solvents from the suspension also maintained the superhydrophobicity. The prepared hybrid micro‐nanocomposite suspensions and hybrid powders were used for various types of applications such as selective oils and organic solvents spill capture, non‐stick and self‐cleaning coatings, selective adsorption of metal ions from metal complex solutions prepared from artificial sea water. Owing to the biocompatibility of the hybrid micro‐nanocomposite powder, this can also be used for various bio‐applications.

Camellia japonica-polysiloxane based superhydrophobic hybrid powder for the selective adsorption of metal ions from a mixture of metal ions in artificial sea water

Superhydrophobic hybrid micro–nanocomposite powder was prepared from a mixture of tannin rich (Camellia japonica) leaf powder, polymethylhydroxysiloxane and phenyl substituted silica ormosils. The surface properties, functional groups, and thermal stability of the hybrid material were analysed by various characterization techniques. The hybrid powder exhibited a hierarchical surface morphology, mesoporous structure, higher thermal stability and superhydrophobicity. The superhydrophobic powder was evaluated for its potential use in the adsorption of metal ions from a mixture of metal ions solutions prepared in artificial sea water. The hybrid material adsorbed copper (II) and nickel (II) ions preferably compared to other competitive metal ions in the mixture solution. The metal ions adsorbed by the superhydrophobic materials were also checked using other leaf powder hybrid materials. The results showed that the preferable adsorption of metal ions can vary according to the type of leaf powder used in the hybrid system.

A comparative study on selective adsorption of metal ions using aminated adsorbents

It is well-known that chitosan consists of amino groups for the chelation of metal ions while NH2-MCM-41 has excellent adsorption selectivities for metals. This work compares both adsorption capacities and selectivities of chitosan and NH2-MCM-41. It has been found that chitosan has adsorption capacities of 1.76mmol/g, 1.03mmol/g and 1.30mmol/g for Cu2+, Ni2+ and Zn2+ respectively whereas NH2-MCM-41 has adsorption capacity of 1.52mmol/g, 0.8mmol/g and 0.83mmol/g for Cu2+, Ni2+ and Zn2+. The higher adsorption capacity in chitosan is attributed to its higher loading of amine groups. The single component adsorption isotherms were well-fitted using Freundlich model. The binary adsorptions of Cu2+–Zn2+ and Ni2+–Zn2+ systems showed similar adsorption selectivities for both adsorbents. However, chitosan has no preferential adsorption for Ni2+–Zn2+ system while NH2-MCM-41 has a good selectivity towards Zn2+. It is believed that the difference can be attributed to the heterogeneous surface of chitosan due to its organic nature. The multi-component adsorptions were best described by a multicomponent extended Freundlich model. Despite the surface functional group, this work indicates the importance of the adsorbent support on selective adsorption.

Synthesis of new chelating ion exchange resins derived from guaran and divinylbenzene styrene copolymer for selective adsorption of metal ions

New chelating ion exchange resin containing hydroximate of 5 amino salicylic acid was synthesized by incorporating it in divinylbenzene styrene (DVBS) copolymer. Hydrophilic polysaccharidematrix ofguaran was also used to incorporate hydroximate of 5 amino salicylic acid in it. The resin characteristics were studied by determining its bulk density, specific bulk volume, moisture content, degree of substitution and ion exchange capacity. The resin was characterized by means of IR spectra, Nitrogen content and pH titration. The distribution coefficient values of different metal ions namely Fe(II), Cu(II) , Zn(II) , Cd(II) , Co(II) , Ni(II), Ca(II), U(VI), Cr(VI) & W(VI) was carried out on these resins as a function of pH . Metal analysis was done by Atomic Absorption Spectrophotometer. The hydroximate derivative of guaran is found to be more selective than that of diving benzene co-polymer.

Selective Adsorption of Metal Ions on Novel Chitosan-Supported Sulfonic Acid Resin.

A novel chitosan-supported sulfonic acid resin modified by propane sultone was prepared and the adsorption characteristics of metal ions are examined by using a crosslinked chitosan-supported sulfonic acid resin (PSC) and a crosslinked chitosan resin (CLC).In the low acidity region, the metal selectivity of PSC is similar to that of CLC. This suggested that the selectivity of PSC was attributed not to the sulfonate group but to the chitosan matrix. The role of the sulfonate is believed to be enriching the metal concentration in the neighborhood of the chitosan matrix. At the same time, since the hydrogen ion is also enriched in a thin layer near the surface of the main, the characteristic adsorption curves of PSC shift to the high pH region compared with those of CLC. The adsorption equilibrium constants of metal ion on PSC and CLC are evaluated. The maximum adsorption capacity for PSC in the case of adsorption of copper is 1.6 times that of CLC. On the other hand, in the high acidity region, the maximum adsorption capacity for PSC in the case of adsorption of palladium is lower than that for CLC because of steric hindrance.

Determination of trace metals in sediments by preconcentration as Xanthogenate complex on activated carbon/AAS.

The selective adsorption of metal ions with activated carbon(AC) and potassium ο-ethyl dithiocarbonate (potassium Xanthogenate) was studied for the preconcentration of traces of Cd(II), Pb(II), Cu(II) and Co(II) ions. To the sample solution of about 100 cm3, 120 mg of potassium Xanthogenate and 50 mg of AC were added, and the mixture was stirred for 20 min in a ultrasonication bath and filtered. AC was heated with 1 cm3 of concentrated nitric acid. After nitric acid was evaporated, adsorpted metals were desorbed in the bath using 5 cm3 of 3 mol dm-3 nitric acid and the AC was removed by filtration. The concentrations of the metal ions in the solution were measured by AAS. The proposed method was successfully applied to the determination of the trace metals in bottom sediments such as pond(NIES, No. 2), river and marine environment by AAS. The results obtained for pond sediment were in excellent agreement with certified values. This method is very simple, and suitable for the determination of trace amounts of Cd, Cu, Pb and Co in the sample containing large amounts of Fe and Al.

Selective adsorption of metal ions on poly(4‐vinylpyridine) resins in which the ligand chain is immobilized by crosslinking

AbstractChelate forming resins (3) were prepared by crosslinking poly(4‐vinylpyridine) (1) with 1,4‐dibromobutane (2) and their complexation with metal ions was studied. Stability constants (K) were found to be much higher for the Cu‐3 system than for the Cu‐1 system, which indicates that 3 uptakes Cu ions with high efficiency. K and the adsorption capacity of Cu decrease largely with increasing degree of crosslinking. Visible and ESR spectra of Cu‐3 show that the structure of the Cu complex within 3 is the same as that of the monomeric Cu‐pyridine complex. However, the ligand‐chain is immobilized in the highly crosslinked 3c and 3d, so that the square planar structure of a stable Cu complex is distorted. The amount of adsorption of Cu, Fe, Cr, Ni, and Zn ions on 3 decreases with the crosslinking, but the adsorption of Hg ions is independent; i.e. 3d selectively adsorbs Hg ions. Metal complexed 1 was crosslinked according to Scheme 1 and the metal ion which was used as template is well adsorbed by the obtained 3. It is considered, therefore, that the ligand chain is maintained at the best conformation for the template ion.